Effect of an Extract of the Root of Scutellaria baicalensis and its Flavonoids on Aflatoxin B₁ Oxidizing Cytochrome P450 Enzymes

Abstract

The inhibition of aflatoxin B₁ (AFB₁) metabolism by a water extract of the root of Scutellaria baicalensis and its flavonoids was examined in liver microsomes. AFB₁ is known to be metabolized to aflatoxin M₁ (AFM₁), aflatoxin Q₁ (AFQ₁), and AFB₁-8,9-epoxide (AFBO). The water extract potently inhibited the production of AFM₁ by cytochrome P450 (CYP)1A1/2 and slightly reduced AFBO formation by CYP1A1/2, CYP2B1, CYP2C11 and CYP3A1/2 in TCDD-treated rat liver microsomes. IC₅₀ values for AFM₁ and AFBO formation were 6.8 and 122.4 μg/ml, respectively. Wogonin showed the highest inhibitory activity towards AFM₁ formation among the flavonoids isolated from the extract. On the other hand, the extract had no effects on the formation of AFBO and AFQ₁ in human liver microsomes, and on the activities of CYP2B1, CYP2C11 and CYP3A1/2 which were detected by hydroxylation patterns of testosterone. These results demonstrated that the extract of the root of Scutellaria baicalensis has a specific inhibitory effect on CYP1A1/2 among CYP enzymes involved in AFB₁ metabolism by rat and human microsomes.

Key words

Scutellaria baicalensis - Labiatae - flavonoid - aflatoxin B₁ - cytochrome P450 1A1/2 - testosterone

References

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